The invention pertains to the field of window framing for commercial, industrial and residential windows, and in particular, to extended frames for single or multiple glazed windows. For many years window frames constructed of extruded aluminum have been widely available for commercial and residential buildings. Such frames are weather resistant for extended periods of time. In particular, they are resistant to moisture, heat and solar ultraviolet degradation. The aluminum framing, however, is highly heat conductive and severely degraded and corroded by salt mist at seashore locations.
With the exception of marine window frames, such as that disclosed in U.S. Pat. No. 3,868,789, window frames constructed of extruded plastics have not become generally available in the marketplace. U.S. Pat. No. 4,110,942 illustrates a polyvinyl chloride extruded window frame mullion with appendages that may be selectively trimmed, depending on the position of the frame member in the window.
Until recently, most plastics suitable for extrusion have been severely degraded by ultraviolet radiation or otherwise structurally inadequate for window frames. Conversely, most plastic materials that have been resistant to ultraviolet degradation have been unsuitable for extrusion or otherwise unsuitable as the structural component of window frames.
U.S. Pat. No. 4,189,520 and U.S. Pat. No. 3,703,063 each disclose composite structural window frame members. The former patent discloses an extruded plastic structure covered with a thin layer of polymethylmethacrylate as a protective coating exposed to the outside ambient conditions and intended to prevent degradation of the underlying structural plastic shape. The latter patent discloses hollow closed metal sections as the structural members with an outer shell of synthetic material formed with one or more projections to accommodate the glazing and the seals adjacent to the glazing. The above composite window framing utilizes complicated cross sectional shapes. Relatively expensive production methods are required to manufacture the composite structure.
In U.S. Pat. No. 3,703,063 a substantially complicated dual frame structure with additional special joining parts is disclosed for between-pane mullions. The profile members disclosed do not serve as both peripheral frame members and mullions in this window framing system because they cannot be assembled with glass retainers to be either symmetric or asymmetric depending on the purpose for which the members are used. The separate means to retain the glazing in position requires two separate extrusions, one of which must be either cemented or otherwise fastened to the frame member permanently before the glazing is placed and the retaining member snapped into place. In U.S. Pat. No. 4,189,520 the T-shaped extrusion that serves as the structural support includes means to retain a separate glazing retention structure comprising four extrusions to each side of the structural shape.
U.S. Pat. No. 3,455,080 discloses a lightweight window frame comprising two snap together extrusions adapted to hold a single pane. Where mullions are located between panes of glass, dual snap together extrusions both of a different profile from that of the peripheral snap together extrusions are disclosed.
U.S. Pat. No. 3,758,997 discloses a metal window framing system with each complete mullion comprising multiple extrusions. Separate dual extrusions including a seating member and a retaining member are required to retain building panels or glazing to each mullion.